Such devices are known, e.g., from Sergeström, U.S. Pat. No. 5,663,718, issued Sep. 2, 1997 and incorporated herein by reference, Patent Application PCT/SE93/00666, which discloses a device intended to be located on a line for electrical high voltage by a crane or helicopter. This device comprises a number of means for remotely controlled, automatic measurement of physical data at a joint in the line. The device shows, however, some limitations as to the measurement methods, as only pointed elements are provided for electrical measurements.